Enabling or disabling defrag

You can modify the defrag utility to meet Vertica configuration requirements, or to optimize your system performance by workload.

On all Red Hat/CentOS systems, you must disable the defrag utility to meet Vertica configuration requirements.

For SUSE 15.1, Vertica recommends that you enable defrag for optimized performance.

Recommended settings by workload for Red Hat/CentOS and SUSE 15.1

Vertica recommends defrag settings to optimize performance by workload. The following table contains recommendations for systems that primarily run concurrent queries (such as short-running dashboard queries), or sequential SELECT or load (COPY) queries:

Operating System	Concurrent	Sequential
Red Hat/CentOS	Disable	Disable
SUSE 15.1	Enable	Enable

See Enabling or disabling transparent hugepages for additional settings that optimize your system performance by workload.

Disabling defrag on Red Hat/CentOS and SUSE 15.1

Determine if defrag is enabled by running the following command:
```
cat /sys/kernel/mm/transparent_hugepage/defrag
[always] madvise never
```
The setting returned in brackets is your current setting. If you are not using madvise or never as your defrag setting, then you must disable defrag.

Edit /etc/rc.local, and add the following script:

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
    echo never > /sys/kernel/mm/transparent_hugepage/defrag
fi

You must reboot your system for the setting to take effect, or run the following echo line to proceed with the install without rebooting:

# echo never > /sys/kernel/mm/transparent_hugepage/defrag

If you are using Red Hat or CentOS, run the following command as root or sudo:
```
$ chmod +x /etc/rc.d/rc.local
```

Enabling defrag on Red Hat/CentOS and SUSE 15.1

Determine if defrag is enabled by running the following command:
```
cat /sys/kernel/mm/transparent_hugepage/defrag
[never] madvise never
```
The setting returned in brackets is your current setting. If you are not using madvise or always as your defrag setting, then you must enable defrag.

Edit /etc/rc.local, and add the following script:

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
    echo always > /sys/kernel/mm/transparent_hugepage/defrag
fi

You must reboot your system for the setting to take effect, or run the following echo line to proceed with the install without rebooting:

# echo always > /sys/kernel/mm/transparent_hugepage/defrag

If you are using Red Hat or CentOS, run the following command as root or sudo:
```
$ chmod +x /etc/rc.d/rc.local
```